1. Technical Field
The invention relates to a process for washing linen or clothes using a washing machine equipped with a rotary drum having a substantially horizontal axis, internally defining two compartments separated by a radial partition passing through said axis.
The invention also relates to a clothes or linen washing machine performing said process.
The linen washing process and the washing machine according to the invention are more particularly applicable to industrial and semiindustrial washing installations, in which relatively large linen loads are treated during each washing cycle.
2. Prior Art
In industrial and semi-industrial washing installations, use is frequently made of washing machines in which two linen loads are simultaneously placed in two compartments of a rotary drum having a substantially horizontal axis. In such washing machines, the two compartments are subdivided by a radial partition passing through the drum axis.
In existing washing machines of this type, the linen is washed by rotating the drum by means of an electric motor controlled by a microprocessor through a speed controller. On starting up, the rotation speed of the drum progressively increases in accordance with a given gradient until a predetermined speed level is reached. This speed level is normally preset in the factory. It corresponds to an angular drum speed such that the linen is subject to a radial acceleration G, which is generally between 0.4 and 0.5 g, in which g represents the gravitational acceleration.
As can be gathered from the attached FIGS. 1A and 1B, the characteristics of such a washing machine do not ensure an efficient washing of the linen.
In FIGS. 1A and 1B references 1 and 2 respectively designate the tank and drum of a washing machine of the aforementioned type. The drum 2 is internally subdivided into two compartments 3a, 3b by a radial partition 4 passing through the substantially horizontal axis of the drum. A linen load 4a, 4b is respectively placed in each of the compartments 3a, 3b. 
When the drum 2 rotates about its axis in the direction of the arrow F1 in FIGS. 1A and 1B, each of the linen loads 4a, 4b is simultaneously subject to the force of gravity Pa, Pb, centrifugal force Ca, Cb and to reaction forces exerted by the walls. Due to the relatively limited angular speed of the drum 2, the vertically downwardly oriented force of gravity Pa, Pb significantly exceeds the centrifugal force Ca, Cb, which is radially oriented towards the outside.
Under these conditions, when the radial partition 4 passes through a substantially horizontal state, the linen loads 4a and 4b, then respectively located in the upper compartment 3a and the lower compartment 3b, occupy the positions illustrated in FIG. 1A. More specifically, the linen load 4a is then placed in the angle formed between the partition 4 and the circumferential wall of the drum 2 on the upstream side with respect to the rotation direction F1 of the latter. The linen load 4b in the lower compartment 3b rests on the circumferential wall of the drum 2, at a location relatively close to the angle formed between said wall and the partition 4 on the downstream side with respect to the rotation direction F1.
As illustrated in FIG. 1B, as the rotation of the drum 2 continues in the direction of the arrow F1, the partition 4 is progressively inclined in the same direction. Bearing in mind the relatively limited nature of the centrifugal force applied to the linen compared with the weight thereof, the linen load 4a in the upper compartment 3a then descends progressively by simply sliding (arrow FG) along the partition 4 to the angle formed between said partition and the circumferential wall of the drum 2 on the downstream side relative to its rotation direction F1. At the same time, the linen load 4b in the lower compartment 3b progressively descends along the circumferential wall of the drum 2, whilst rolling on itself (arrow FR), until it is placed in the angle or corner formed between said wall and the partition 4 on the upstream side with respect to the drum rotation direction F1.
In existing washing machines of this type, the rotation of the drum 2 consequently leads to a mere displacement of two linen loads 4a, 4b successively by sliding along the radial partition 4 and by sliding and rolling along the circumferential wall of the drum 2.
However, it has been established that the washing efficiency of a washing machine is essentially due to the number of drops, falls or tumbles undergone by the linen within the rotary drum and the height thereof. More specifically, washing is more efficient as the linen undergoes a higher number of drops over as great a height as possible. From this standpoint, existing washing machines where the tank is subdivided into two compartments by a radial partition have a relatively unsatisfactory washing efficiency.
It should be noted that this problem is specific to washing machines, whose tank is subdivided into two compartments by a radial partition. Thus, at the normal rotation speed of the drum, said partition essentially opposes any drop of the linen, as has been explained relative to FIGS. 1A and 1B. In washing machines lacking such a partition and for the same drum rotation speed, the single linen load contained therein is subject to repeated drops.
Moreover, it is important to note an xe2x80x9corbitingxe2x80x9d of the linen, i.e. its locking against the circumferential wall of the drum when the latter performs a complete turn or revolution must be avoided. Such a phenomenon arises when the radial acceleration G applied to the linen reaches 1 g.
The invention relates to a process for washing linen using a washing machine having two compartments and which makes it possible to very significantly improve the efficiency of washing without any risk of the linen orbiting.
According to the invention, this result is obtained by means of a process for washing linen, wherein:
the linen is placed in two compartments defined within a rotary drum, which has a substantially horizontal axis, by a radial partition passing through said axis and
the drum is rotated about its axis, characterized in that the drum is rotated at an angular speed such that the linen is subject to a substantially constant radial acceleration G with a mean value between approximately 0.70 g and approximately 0.95 g, where g represents the gravitational acceleration.
By subjecting the linen to such a radial acceleration, it is possible to ensure that each of the two linen loads placed in the drum undergoes a drop on each occasion when the drum rotates by a half-turn. Moreover, each drop takes place over a height close to the diameter of the drum. Thus, an efficient washing of the linen is obtained.
As the angular acceleration to which the linen is exposed remains in all cases below 1 g, there is no risk of linen orbiting.
In a preferred embodiment of the invention, the drum is rotated at an angular speed such that the linen is subject to a substantially constant radial acceleration G, whose mean value is between approximately 0.80 g and approximately 0.90 g.
The drum is preferably rotated at a substantially constant angular speed.
In an embodiment of the invention, the rotation speed of the drum is then measured and a drive motor for the same is controlled so as to make the measured speed substantially constant. This embodiment is more particularly applicable in the case where the motor rotates the drum by transmission means with sliding, e.g. using a smooth belt.
In another embodiment of the invention, applied to the case where the drum is rotated by a motor through sliding-free transmission means, e.g. using a toothed belt, the rotation speed of the motor is measured and is controlled in such a way as to make the measured speed substantially constant.
The invention also relates to a washing machine comprising:
a rotary drum, which has a substantially horizontal axis, internally defining two compartments separated by a radial partition passing through said axis and
control means for rotating the drum about its axis, characterized in that said control means rotate the drum at an angular speed such that the linen is subject to a substantially constant radial acceleration G, whose mean value is between approximately 0.70 g and approximately 0.95 g, in which g represents gravitational acceleration.